U.S. Pat. No. 3,955,535 illustrates a cow trainer with a switch which isolates cow trainer parts from the electric wire, except when the cow humps her back, whereupon the cow trainer parts are elevated to close the contacts of the switch and connect the cow trainer parts to the electric wire and to impose an electric shock on the cow. The switch illustrated in said patent is relatively expensive to fabricate and is subject to fouling with dirt, rust and corrosion. Moreover, said switch relies entirely upon gravity to open the switch. Hence it may become unreliable in operation after a prolonged period of use in a cow barn environment.